Wireless communication technology has evolved greatly over the recent years. Recent studies have shown that the wireless spectrum in U.S. is under-utilized, although most of the spectrum has been assigned to licensees, or primary users. Therefore, spectrum sharing has been proposed to alleviate the spectrum scarcity that prevents new wireless services being deployed. Cognitive radio is a promising technology that can allow secondary usage of spectrum without causing harmful interference to the primary systems. The secondary users, or cognitive radios, are required to perform spectrum (channel) sensing before accessing a channel that has been assigned to a licensed or primary user.
In order to reliably detect the primary signal, an individual radio needs to have very high sensitivity to offset the fading and shadowing conditions of a radio channel. To overcome the difficulties that an individual radio experiences in determining channel occupancy, cooperative sensing is proposed to improve the performance of detection. For a more detailed discussion on cooperative sensing see S. M. Mishra, A. Sahai, and R. W. Broderson, “Cooperative sensing among cognitive radios”, Proc. IEEE ICC 2006, Istanbul, Turkey, June, 2006 and A. Gashemi and E. Sousa, “Impact of user collaboration on the performance of sensing-based opportunistic spectrum access”, Proc. IEEE VTC 2006, pp. 1-6, Fall 2006, both of which are hereby incorporated by reference in their entireties.
In cooperative sensing, the final decision is made by a central node using the sensing data collected by the distributed radios. Although there have been many publications related to cooperative sensing, there is no systematic method on how to dynamically allocate the spectrum sensing resources: such as the sensing time for each candidate channel; the number of radios need to be included in collaborative sensing, and other spectrum sensing resources.
Therefore a need exists to overcome the problems with the prior art as discussed above.